1. Field of the Invention
The present invention generally relates to a data recording and/or reproducing apparatus in a data transmission system using a command, and in particular to a system and method of processing an equipment control command sent from an external equipment via a digital interface defined by such as IEEE 1394 Standard for controlling a data recording and/or reproducing apparatus having an optical disk drive, magnetic disk drive and the like.
2. Description of the Prior Art
Recently, use of IEEE 1394 Standard has been increased as a digital interface in a serial data transmission system. The IEEE 1394 system can be used not only for transmission of computer data which is conventionally conducted by a SCSI system or the like, but also used for transmission of substantive audio and/or video (referred to as xe2x80x9cAVxe2x80x9d, hereinafter) data to be processed by an AV equipment. This is because the IEEE 1394 system has two communication methods defined therein, i.e., an isochronous data transmission system and an asynchronous data transmission system.
The isochronous communication is a data transmission method which can be used for transmitting such as substantive AV data requiring a real time property. In this method, a frequency band required for the data transmission is previously obtained prior to the start of the data transmission, and then the data transmission is conducted using the band. By this arrangement, the real time property of the data transmission can be assured.
Meanwhile, the asynchronous communication is a data transmission method using a free time for transmitting auxiliary data such as command or computer data and the like which does not require a real time property. This communication method can be regarded as equivalent to a conventional SCSI method.
Various standards are proposed as a host transmission protocol on the IEEE 1394 system, and IEC 61883 standard is used as one of the methods. The IEC 61883 standard specifies a method of sending and receiving AV data requiring real time property in an isochronous communication system and also specifies a method of sending and receiving a command to be given to an AV equipment in an asynchronous communication system. A set of AV/C commands and responses are transported by Function Control Protocol (FCP) defined by IEC 61883 standard. FCP provides a simple method for encapsulating commands and responses within IEEE 1394 standard.
When the equipment is controlled by the command transmitted on IEC 61883 standard, there may occasionally arise a request for canceling the last executed command. For example, a desire is raised in the following case where audio data is recorded on a plurality of audio tracks formed on an optical disk and a certain audio track data is once deleted and thereafter the executed delete operation per se is required to be canceled so that the deleted audio track data is restored.
However, in the conventional command processing system, when the equipment is controlled by a plurality of controllers, the user cannot know which controller has sent the command of the last control to the equipment. When a certain external controller sends a command to cancel the last executed operation to the equipment, the user can not know whether the control to be canceled is the last control executed by this command source controller. Moreover, in some equipment, the last several commands can be canceled, and in such a case it is necessary to know what kind or item of commands is to be canceled. However, in the conventional system, there is no method for the user to know the contents of commands to be canceled.
Moreover, when an optical disk is loaded on a data recording/reproducing apparatus, management information, such as attributive data, is reproduced and stored as a management information list in a management storage portion of the apparatus. Meanwhile, status information indicating the present operation status of the apparatus such as reproduction or stop, present reproduction position, present reproduction method such as normal reproduction or program reproduction and the like, are stored as a status information list in a status storage portion of the apparatus.
When the user desires to know the contents of the present operation status information of the apparatus, the desired status information of the apparatus can be obtained by accessing the target information list, and the user obtains the contents of the status information as to what status the apparatus operating at present, via the digital interface.
In the conventional system, however, since the contents of the status information are arranged in a fixed manner in bytes, when accessing to the contents of the status information contained in the list, the accessing position in bytes must be designated from the top position in the list. Therefore, if an input of the information contents is erroneously performed even in one byte position in the list, the resultant content is undesirably different from the exact content position. In this undesirable case of erroneous byte position, it is difficult for the external equipment to confirm the erroneous byte position because the external equipment confirms the information list read out from the apparatus as a series of a byte sequence.
In order to achieve the objects mentioned above, the present invention provides a command processing system for processing an equipment control command sent from external equipment via a digital interface, which the system comprises: a system control that receives and executes the command to process management information of main data based on the received command; and a status/command storage that stores the last executed commands processed by the system control, wherein the system control informs the external controller of contents of the last executed commands stored by the status/command storage in response to the command from the external controller.
The present invention has been developed to solve these problems inherent to the conventional command processing system, and an essential object of the present invention is to provide an improvement of a command processing system and method thereof in which the user can easily know the content of the last control command provided for controlling equipment.
Another object of the present invention is to provide an improvement of a command processing system and method thereof using a specific command adapted thereto, which is capable of storing command contents together with status information contents in a list format, and easily capable of reading the command contents and status information contents from a precise position when accessing thereto.
In order to achieve the objects mentioned above, the present invention provides a command processing system for processing an equipment control command sent from an external equipment via a digital interface, which the system comprises:
a system control means receiving the command and executing the command to process management information of main data based on the received command; and
a status/command storage means for storing the last executed commands processed by the system control means,
wherein the system control means informs the external controller of contents of the last executed commands stored by the status/command storage means in response to the command from the external controller.
In this construction, the equipment is a data recording and reproducing apparatus having a recording medium in which the main data and management information are recorded thereon and reproduced therefrom.
The system further comprises a management information storage that stores the management information just before and just after execution of the received command by the system control.
The status/command storage means stores the status information indicative of the present operation status of the equipment together with the last executed command. The equipment further comprises a list producer that produces a list of the status information including the last executed command therefrom.
According to another aspect of the present invention, a command processing method for processing a command sent from an external controller to an equipment via a digital interface, comprises: receiving the command and executing the command to process management information of main data based on the received command; storing the last executed commands processed by the command execution; and informing the external controller of contents of the last executed commands stored by the command storage, in response to the command from the external controller.
By this arrangement, all or a part of the management information in the recording medium just before the execution of the command and the command issued from the controller are stored for the execution of the command issued to the equipment. When the equipment receives the command to cancel the last command from the controller, the last management information is restored from the stored management information. The management information can be thereby restored to the status which it had, just before the execution of the command. When the controller inquires about the contents of the stored commands, the contents of the inquired command are outputted to the controller.
In the method of the present invention, when the controller issues the command to cancel the last command over the equipment, the equipment informs the controller of no command to be canceled if there is no command to be canceled. When the controller attempts to change the last command held in the equipment, the equipment rejects the command to change the last command.
Moreover, even when a list of the equipment control command content and/or status information content is renewed, it is not necessary to identify a byte position of the renewed content in the list, and therefore a desired command and/or status information can be easily accessed by way of the same designation method, and whereby a user can obtain a list of the last executed command and status information of the apparatus by a simple construction and method.